Self-locking drop-door

ABSTRACT

A drop-door hinged at the bottom to an enclosure, and having support bars pivotally connected to the door and slidable through slots in the enclosure adjacent the opening closed by the door. The support bars are angular, with short arms adjacent the door to move into the slots in the enclosures, and counterweight arms to move about the bottoms of the slots in the enclosures as fulcrums to assume downwardly depending self-locking positions.

United States Patent Inventor Homer G. Woten 912 Perrin Ave. N. W.,Winter Haven, Fla. 33880 Appl. No. 821,714 Filed May 5, 1969 PatentedMay 18, 1971 SELF-LOCKING DROP-DOOR 4 Claims, 5 Drawing Figs.

U.S. Cl 49/387, 296/57 Int. Cl E05f 1/00 Field of Search 296/50, 57;49/3 87 [56] References Cited UNITED STATES PATENTS 474,353 5/1892Bailey 296/57 1,270,695 6/1918 Carlson 296/57 3,063,747 11/1962 Anderson296/57 Primary Examiner-Kenneth Downey Altorney-Mason, Fenwick &Lawrence ABSTRACT: A drop-door hinged at the bottom to an enclosure, andhaving support bars pivotally connected to the door and slidable throughslots in the enclosure adjacent the open-- ing closed by the door. Thesupport bars are angular, with short arms adjacent the door to move intothe slots in the enclosures, and counterweight arms to move about thebottoms of the slots in the enclosures as fulcrums to assume downwardlydepending self-locking positions.

PATENTEU am a 197i BY Wm HOMER. G WOTEN BACKGROUND OF THE INVENTION Thisinvention relates to self-locking, hinged closures, and particularly toself-locking drop-door supports.

The conventional drop-door construction, whether it be an access doorinto a building or machine housing, or a vehicle tailgate, consists of arectangular door which is hinged at its bottom to the building, housing,etc., and has some means to hold it at an open position, usuallyhorizontal at right angles to the opening it closes. The holding, orsupport, means normally consists of a chain or hinged brace secured tothe wall adjacent the opening and to the door, to support the door inthe open, horizontal position.

The usual support member is incapable of holding the door in its raised,closed position, and some other means must be employed for this purpose.Many types of locks, latches, hasps, etc. have been used to accomplishthis. Obviously, the door must be held in its raised position while thelock, or similar device, is fastened, and the holding means must bereleased before the door can be lowered.

SUMMARY OF THE INVENTION The object of the present invention is toprovide a dropdoor having support means which will automatically holdthe door in predetermined open position when lowered and automaticallyhold the door in closed position when raised.

Another object of the invention is to provide such means which can bedesigned to hold the door closed with sufficient force to requireconsiderable pull to open it, or so designed that a light pull is allthat is necessary to open the door.

A further object is to provide a door support which can counterbalancethe door to hold it in some intermediate positron.

Yet another object of the invention is to provide a dropdoor supportwhich is extremely simple, yet can be made to withstand great loads andoperate very smoothly and easily.

Other objects of the invention will become apparent from the followingdescription of one practical embodiment thereof, when taken inconjunction with the drawings which accompany, and form part of, thisspecification.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of adrop-door and support means embodying the principles of the presentinvention, with part of a representative housing on which the door ismounted being shown;

FIG. 2 is a view similar to FIG. I, but with the door in loweredposition;

FIG. 3 is a vertical section taken on the line 3-3 of FIG. 1;

FIG. 4 is a similar view to FIG. 3, but with the door in loweredposition; and

FIG. Sis a perspective view of one of the new support members.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawings indetail, the door I of the present invention is shown in conjunction witha housing 2, which is representative of any type of walled structureinto which the door 1 is designed to provide access. The housing has anopening 3 which the door is designed to cover when in closed positron.

The door is shown as a rectangular member 4 of such proportions as tofit within the opening 3 in the housing. Plates 5 are mounted along thesides of the main door portion 4, and project outwardly beyond the sidesto provide flanges 6 to abut the wall of the housing about the opening 3and limit the inward movement of the door. Plates 5 terminate short ofthe bottom of the door, so that when the door is open they will notconflict with an outwardly projecting ledge 7 along the bottom of theopening 3. The ledge fonns a mounting surface for hinges 8 which connectthe door to the housing, and also as a rear support means when the dooris lowered to relieve the hinges of the weight of the door and any loadwhich may be supported upon it. Two or more hinges may be used, as

required, and the hinges are attached to the bottom portion of the doorand to the ledge 7.

Each side flange 6 has an elongated slot 9 near its top, the slotextending longitudinally of the flange, and there is a mounting bearing10 secured upon the outer faces of the flanges 6 overlying the slots 9.Each bearing plate has a pair of spaced, upstanding ears l1, and thereis a slot 12 in each bearing, similar to the slots 9 in the flanges 6and overlying the slot 9 of its respective flange.

One end of a support bar 13 extends through each pair of aligned slots 9and 12, and pins 14 project transversely from the end and are journaledin the ears ll of the bearing plate. This provides for pivotal mountingof the bars 13 relative to the door. The opposite ends of the bars 13pass slidably through slots 15 in those portions of the sidewall of thehousing 2 overlapped by the flanges 6 when the door is in closedposition. Slots 15 will be in underlying alignment with the slots 9 and12 when the door is in its raised, closed position. Transverselyextending pins 16 at the rear ends of the bars abut the inner surface ofthe housing wall at the sides of the slots 15 when the door is in itslowered, open position, and form stops to limit the downward movement ofthe door.

It will be noted from the drawings that the support bars 13 areelongated, straight members for the major portion of their lengths, toprovide counterweight arms 17, and there are short, angularly offsetlocking arms adjacent the pins 14 and movable within the slots 9 and 12,and also in the slots 15 when the door is in closed position. Thelengths of the locking arms 18 relative to the thickness of the variousparts at the door area determine the downward angle of the arms 17 whenthe door is in raised position, and this angle, together with the weightof arms 17, detennines the closure force exerted by the arms 17 tomaintain the door in closed position.

When the door is in use, and in its open position as shown in FIG. 2,the support bars will be fully drawn through the slots 15 in thehousing, and the pins 16 at the rear ends of the slides will be inabutment with the backface of the housing wall. In this position, thebars act as diagonal braces to support the door from points well abovethe hinge line of the door. This will provide the same support as wouldconventional chains or hinge braces. When the door is raised, however,the bars begin to slide through the slots 15, with the front ends of thebars freely pivoting in the bearing plates 10. When the door isapproximately half raised, the counterweight arms 17 of the bars willoccupy the position shown in dotted lines in FIG. 4. Continued movementof the door in an upward direction will first I bring the arms 17 to ahorizontal position, and then the arms will begin to assume a slightlydownward tilt. After the arms 17 have reached the horizontal position,the weight of the arms will serve to counterweight the door, and thedoor may be stopped in some intermediate positions. As the doorapproaches its closed position, however, the bars move inwardly to thepoint where the inner angle 19 between the arms 17 and 18, reaches theslot 15 and counterweight arms 17 of the bars begin to move rapidlydownward. When this position is reached, the weight of the arms 17 willdraw the door to its completely closed position and will be sufficientto hold the door closed.

The closure force exerted by the support bars can be varied to suitspecific means. This can be done in either of two ways, or by means of acombination of the two. The first manner in which the force can beincreased is by increasing the weight of the counterweight arms 17 ofthe support bars. The greater the weight of the arms, the more pull onthe door in an opening direction will be required to cause the arms toswing upwardly, while moving about the bottom edges of the slots 15 asfulcrums. The heavier the weight of the arms, the greater the forcewhich will be applied to automatically bring the door to its closedposition and the support bars into their locking positions. The secondmanner of increasing the locking force is by changing the lengths of thelocking arms 18 so as to allow the arms 17 to assume positions morenearly vertical when the door is in closed position. The closer the arms17 approach the vertical, the more force will be required to swing themupward about their fulcrums on the lower edges of the slots 15. Thelighter the weight of the arms 17 and the greater their angle from thevertical when in final locked position, the easier the door will be tomove from its closed position.

A door having the support means of the present invention can be openedsimply by pulling the door from its closed position and moving it aboutits hinges. When the door reaches a horizontal position, the supportbars will have reached their limit of travel and will serve as braces tomaintain the door in that position and support any load which may be putupon it. When the door is raised to a position close to the fully closedposition, it will automatically move to its fully closed position andthe support bars will hold the door against accidental opening.

Iclaim:

l. A self-locking drop-door for a wall having an opening comprising, adoor proper, hinges pivotally connecting the bottom of the door properto the wall adjacent the bottom edge of the opening, and a support barpivotally connected at one end to the door proper by pivot connectormeans at a point spaced from the bottom of the door proper, the wallhaving a slot through which the support bar slidably passes with thelock bar having a lower edge resting on the lower edge of the slot withthe slot being adjacent the opening and at a distance from the hingesequal to the spacing from the hinges to the connection of the supportbar to the door proper, the support bar being angular in shape andcomprising a short locking arm having said pivot connector means on oneend pivotally connected to the door proper and a long counterweight armextending angularly from the other end of said short locking arm so thatsaid pivot connector means is not in alignment with the axis of saidcounterweight arm, stop means on the end of said counterweight armopposite said locking arm dimensioned and oriented so as to be incapableof passage through said slot, the locking arm being no longer than thedistance from the pivotal connection of the locking arm to the doorproper to the inside of the wall when the door proper is in raisedclosed position, and the angle between the locking arm and thecounterweight arm being such as to position the counterweight arm at aninclined angle to said wall when the door is in its raised closedposition so that the weight of said counterweight arm acts to provide aholding force on the door to hold the door in its raised closed positionwhereby an opposite opening force exerted on the top of the door inexcess of the holding force in a door opening direction causes saidcounterweight arm to pivot upwardly while simultaneously slidingoutwardly of said slot until said stop means engages the wall adjacentthe slot to enable a full opening of movement of said door.

2. A self-locking drop-door as claimed in claim 1, wherein, there is asupport bar pivotally attached to each side of the door proper andslidable through a slot at each side of the opening.

3. A self-locking drop-door as claimed in claim 2 wherein said stopmeans comprises transversely extending pin means on the support bars toengage the wall adjacent said slots to limit the sliding movement of thesupport bars and the downward swinging movement of the door proper.

4. A self-locking drop-door as claimed in claim 3 wherein, thecounterweight arm is of sufiicient length to allow the door proper toopen to horizontal position before said pin means engages the wall.

1. A self-locking drop-door for a wall having an opening comprising, adoor proper, hinges pivotally connecting the bottom of the door properto the wall adjacent the bottom edge of the opening, and a support barpivotally connected at one end to the door proper by pivot connectormeans at a point spaced from the bottom of the door proper, the wallhaving a slot through which the support bar slidably passes with thelock bar having a lower edge resting on the lower edge of the slot withthe slot being adjacent the opening and at a distance from the hingesequal to the spacing from the hinges to the connection of the supportbar to the door proper, the support bar being angular in shape andcomprising a short locking arm having said pivot connector means on oneend pivotally connected to the door proper and a long counterweight armextending angularly from the other end of said short locking arm so thatsaid pivot connector means is not in alignment with the axis of saidcounterweight arm, stop means on the end of said counterweight armopposite said locking arm dimensioned and oriented so as to be incapableof passage through said slot, the locking arm being no longer than thedistance from the pivotal connection of the locking arm to the doorproper to the inside of the wall when the door proper is in raisedclosed position, and the angle between the locking arm and thecounterweight arm being such as to position the counterweight arm at aninclined angle to said wall when the door is in its raised closedposition so that the weight of said counterweight arm acts to provide aholding force on the door to hold the door in its raised closed positionwhereby an opposite opening force exerted on the top of the door inexcess of the holding force in a door opening direction causes saidcounterweight arm to pivot upwardly while simultaneously slidingoutwardly of said slot until said stop means engages the wall adjacentthe slot to enable a full opening of movement of said door.
 2. Aself-locking drop-door as claimed in claim 1, wherein, there is asupport bar pivotallY attached to each side of the door proper andslidable through a slot at each side of the opening.
 3. A self-lockingdrop-door as claimed in claim 2 wherein said stop means comprisestransversely extending pin means on the support bars to engage the walladjacent said slots to limit the sliding movement of the support barsand the downward swinging movement of the door proper.
 4. A self-lockingdrop-door as claimed in claim 3 wherein, the counterweight arm is ofsufficient length to allow the door proper to open to horizontalposition before said pin means engages the wall.